Various distinct networks exist over which a wireless device can communicate, such as a mobile telephony network (e.g., CDMA, GSM, etc.), a wireless local area network WLAN or WiFi network, a piconet (e.g., Bluetooth). Wireless devices that communicate over multiple such networks are termed herein as multiradio devices, indicative of the multiple radios that such a device incorporates so as to enable communication over multiple networks. For example, a WLAN access point may have a radio for communication with WLAN terminals; a Bluetooth radio to couple with a printer; and a wired or wireless (e.g., Bluetooth, infrared, another WLAN) connection to the Internet. Similarly, a mobile terminal/mobile station may have one GSM modem, a CDMA modem, a Bluetooth modem (e.g., with a headset), and a DVB-H modem. Any individual multiradio device may also have more than one radio for communicating over a single network, such as a mobile station having two GSM radios so as to avoid switching between an active Node B and another Node B in preparation for a handover. Each of these radios has a modem, and “modem” and “radio” will be used interchangeably hereinafter.
More particularly for the modems operating under control of different networks, there is a potential for modems to interfere with one another when transmitting or receiving simultaneously with other modems where the disparate networks use frequency ranges that overlap and each network schedules/authorizes the multiradio device to transmit/receive at an overlapping frequency at the same time. The result is wasted bandwidth due to data collisions from different modems of the same wireless device.
One fundamental difficulty in designing a multiradio device to avoid self-collision among its modems is the ability to interpret any modem's behavior regardless of the clock-domain it uses. Not only do the modems typically have their own hardware clocks with different frequencies as compared to other modems of the same device, but they are also synchronized with their corresponding peer devices (e.g., WLAN with access point, GSM with base station, Bluetooth with an ad hoc peer). As the mobile device is moved around, its modems' synchronization with the respective peer shifts and changes, thus offsetting their transmission instances. The result is that any difference between transmission grant start times on different networks is not constant. The term slot is used herein generically to represent an authorized transmission or reception window. While the term slot is specific to some radio protocols, its use herein does not imply limitation to only those radio protocols that use the term explicitly.
Another difficulty is the nondeterministic nature of delays caused by bus arbitration within the multiradio device. If all the timing-critical functions designed for multiradio control were to be placed in a central processor, the signaling between modems and that central processor becomes the volatile factor that may handicap the entire design concept. At best it makes a software design difficult and reduces its portability among different types of multiradio devices that operate on the same sets of networks, since the different types of multiradios would exhibit different bus arbitration. At worst it generates a substantial load on that central processor due to timer checks and resynchronization calculations caused by inaccurate time information.
Other issues are raised by operation of such multiradio devices. Since it is often impossible to allow more than one radio or modem of the multiradio device to access a common communications resource (such as, for example, a common communications channel) at the same time, access to the common communications resource has to be allocated in some manner. In one conceivable allocation scheme, access to the common communications resource may be allocated in a pre-determined manner, with one modem being allocated a certain percentage of non-concurrent access; another modem being allocated a different percentage of non-concurrent access, etc.
Such an approach, though, may not accommodate transient needs of one of the modems for a higher percentage of access due to, for example, criticality of information being communicated. Although allocation by percentage may be desirable for most situations, it would also be desirable to deviate from this allocation scheme for a temporary period of time. Accordingly, those skilled in the art seek methods and apparatus that are capable of providing such modes of operation.